Most of the time, when a name is given to her, it's "Emma Tybur". Why Emma ? I don't know. But a big part of the fandom uses it, and I use it too (also that's why I find "Mrs Tybur" weird to hear because for me it's like if Emma was her official name).
As an example, if I enter "Emma Tybur" on the research bar, on the first page, I've got :
- A reddit thread, "Comparing her facial structures with Emma Tybur"
- A tumblr tag named "emma tybur"
- A french manga threads where people name her Emma
The other name I've seen for her is a sexual joke based on her brother's name "Willy".
By the way, I have nothing against "Ophelia Tybur", but my mind considers "Emma Tybur" as her official name, so I'll stay with "Emma" x)